Coral Reefs

Take a tour of some of the most biodiverse areas in our oceans. Coral reefs have all types of marine life.

By Underwater Earth

Apo Island

Apo Island, a small volcanic island situated off Negros Island in the Philippines, is a popular destination for snorkeling and diving. Its surrounding marine reserve is home to hundreds of coral species and other sea life, including manta rays and rare hammerhead sharks.

[Tap and drag to look around the reef]

Coral Reefs on the Rebound

The coral reefs here were almost completely devastated over 30 years ago due to poor fishing practices. Fast forward to today, and these are now some of the healthiest reefs in the Philippines due to preservation efforts.

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Deep Reef in the Red Sea

The Red Sea is a long, thin inlet of water that separates Africa from Asia. Its water is exceptionally warm and salty. The Red Sea reefs contain over 200 species of corals. 

The reefs have many characteristics that distinguish them from other coral reefs, including a high level of tolerance for extreme temperatures and extra-salty water. 

Deep Sea Reef

All around you spreads the deep sea reef. These reefs are usually 30–40 meters below the water’s surface, but some are 150-meters deep.  The Red Sea is a relatively shallow body of water, and most of its reefs are near the surface. 

Some former reefs now rise above the surface to form islands.

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Underwater Tourism

The Red Sea reefs are an important tourist attraction, but they are also endangered, not only by tourists but also by pollution and by dredging of the Red Sea to keep shipping channels open.

Aquarius Reef Base

Aquarius is an underwater laboratory located in the Florida Keys. It once belonged to the National Ocean and Atmospheric Administration (NOAA), but Florida International University (FIU) now owns and controls it. 

Aquarius is equipped to allow 2 scientists, called aquanauts, to live for a 10-day period beneath the surface of the ocean. Aquanuts conduct research on coral reefs, climate change and the well-being of the ocean in general.

Research Station

How do scientists and ocean enthusiasts experience and learn about the ocean? Usually by using a self-contained underwater breathing apparatus (scuba). Scuba tanks can run out of oxygen quickly, but this research station allows researchers more time underwater.

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Aquanauts

Just think of everything aquanauts can see and learn while living on the reef around the clock!  Aquanauts become acclimated to the pressure at 62 feet below the ocean’s surface through a technique called saturation diving.

Osprey Reef in the Coral Sea

What would a coral reef expedition be without seeing a shark? Not very exciting! That’s unlikely to happen if you visit the Coral Sea, located between the northeastern end of Australia and the Solomon Islands. 

This area is considered a biodiversity hotspot, with around 52 species of cartilaginous fish, including sharks. Sharks are cartilaginous fish because the only bones in a shark’s body are the jawbone and teeth.

The Shades of Sharks

Notice the sharks’ coloration—their dorsal (top) side is darker than their ventral (bottom) side. This is called countershading. The streamlined shape of their bodies helps them navigate through currents with speed and efficiency.

Threatened Sharks

Across the globe, sharks are threatened due to shark finning. It’s estimated that more than 100 million sharks are killed each year for their fins, which are used in some cultures to make shark fin soup.

Tern Island

North of Hawaii, Tern Island is part of the French Frigate Shoals, which is the largest atoll in the Hawaiian Islands. Atolls are ring-shaped coral reefs that usually contain a lagoon in the center. 

Tern Island is maintained by the Hawaiian Islands National Wildlife Refuge and the United States Fish and Wildlife Service, which actively prevents contaminating the breeding grounds for the terns that live on the island as well as seals.

Beach Birds

Tern Island gets its name from the hundreds of thousands of seabirds that nest there. Some of the resident species include the sooty tern, the grey-backed tern, the brown noddy, the black noddy, the white tern, and the blue-grey noddy.

Landing Strip

Tern Island contains a tiny airport, built by the U.S. Navy after the Battle of Midway during WWII. You can see the landing strip here. Planes coming from Hawaii and headed towards the Midway Atoll landed here from 1942–1946.

Pollution on East Island

In this image, you can see plastic strewn across East Island, southeast of Tern Island. This plastic represents the indirect effects humans have on an ecosystem. Each ocean has a large surface current, called a gyre. 

These currents move in a circular motion, creating a whirlpool effect and gathering up all debris in the water. The Pacific Ocean, the world’s largest ocean, has an enormous patch of plastic floating in the middle of it, the Great Pacific Garbage Patch.

The Path of Pollution

Ocean pollution mainly starts on land—only about 20% of all plastic debris comes from boats. When the plastic enters the water system, it gets transported all around the ocean and can enter the food chain at the lowest level. 

Carysfort Reef

The Florida Keys used to be home to some of the most biodiverse reefs in the world. Due to exploitation, coral disease, and bleaching, however, almost 80% of the reefs have been lost. 

The Florida Keys National Marine Sanctuary, which is the third largest protected area in the United States, protects some of the remaining reef systems. 

Coral Bleaching

The lifeless land around you was one of the most biodiverse in the ocean before it suffered through coral bleaching. Coral bleaching occurs when coral polyps spit out photosynthetic algae (zooxanthellae), which causes the corals to lose color and die.

Coral Temperatures

Even a slight change in temperature—as little as a 2-degree change in water temperature—can cause a bleaching event. Reef ecosystems are more sensitive to physical and chemical change than any other marine ecosystem.

Unhealthy Coral Reef

Since reefs make up 1% of the ocean but are responsible for over 25% of their biodiversity, it makes sense that fish from reefs support coastal communities as well as commercial fisheries. 

Today, people use several different methods for taking fish out of the ocean, but each comes with tradeoffs. Fishing methods can exploit fish populations at different levels of the food web, which can have unpredictable effects. 

Fishing Gear

Sometimes fishing nets like the one here fall from boats onto reefs. Even though they’re no longer being used for fishing, these nets continue to catch fish. Called ghost fishing, this can cause damage to anything in its path.

The Coral Nursery

For years, humans have recognized the problems affecting reefs. Ken Nedimyer was a commercial fisherman who started to notice the decline in reefs in the Florida Keys. 

He recognized that the loss of reef systems would have a huge impact on the local environment and economies worldwide, so he started the Coral Restoration Foundation. The Coral Restoration Foundation began in 2012 by planting 18 elkhorn coral. 

Three years later, all 18 coral are still thriving.

Coral Restoration

The Coral Restoration Foundation grows coral in a lab for 6–9 months and then transplants the new coral into the reef system. Once transplanted, the coral becomes part of the recovering ecosystem, inviting fish and other organisms to the area.

The Underwater Museum of Isla Mujeres

Isla Mujeres, Mexico, a popular tourist destination, is experiencing overexploitation and climate change. This Underwater Museum hopes to combat those pressures and rebuild the reef ecosystem by creating artificial reefs. 

Instead of breeding coral in the lab, an artificial reef tries to recruit existing polyps in the water to attach to a surface that has been transplanted into the water for that purpose. Old boats have been sunk in efforts to create an artificial reef.

Underwater Sculptures

Dr. Jaime Gonzalez Cano and artist Jason deCaries Taylor have designed underwater sculptures that are not only visually inviting but can serve as an artificial community for reef recruitment. Cano and Taylor have built more than 1,000 artificial habitats.

Dive into more Underwater Earth stories, videos and images in our collection.

Credits: Story

AXA XL, Atmosphere Resorts, The University of Queensland, Google, Office of National Marine Sanctuaries, Florida Keys National Marine Sanctuary, Florida International University, Aquarius Reef Base, Coral Restoration Foundation, NOAA, Panedia, Fourth Element

Credits: All media
The story featured may in some cases have been created by an independent third party and may not always represent the views of the institutions, listed below, who have supplied the content.
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